Reviews of Two Programming Books

In this article I review two recent competitive programming books, published in 2020, which have not yet been presented in the Olympiads in Informatics journal. The books are Algorithmic Thinking by Daniel Zingaro and Competitive Programming in Python by Christoph Dürr and Jill-Jênn Vie. Both the books are introductory books but their approaches are different. Algorithmic Thinking focuses on the process of learning algorithmic problem solving and uses competitive programming problems as motivating challenges. Competitive Programming in Python develops skills for programming contests and job interviews, and shows how the Python language can be used in competitive programming.

The Italian Job: Moving (Massively) Online a National Olympiad

The COVID-19 pandemic is having a pervasive effect worldwide, including local, national and international Olympiads in Informatics. Most national Olympiads had to be moved online, a process which poses a number of serious challenges. Help across countries is of uttermost importance in this context, to enable a successful continuation of the IOI during globally hard times. In this paper, we share the experience gained and tools produced during a year of online Olympiads in Italy, hoping that other countries can take profit of these (freely available) tools and suggestions for their own Olympiads.

Look Ma, Backtracking without Recursion

I show how backtracking can be discovered naturally without using a recursive function (nor using a loop with an explicit stack). Rather, my approach involves a form of self application that can be elegantly expressed in an object-oriented program, and that is reminiscent of how recursion is done in lambda calculus. It also illustrates why reasoning about object-oriented programs can be hard.

Security of Grading Systems

Programming contests often employ automatic grading of solutions. Graders need to run potentially malicious code, which brings many security issues. We discuss various attacks on grading system security and suggest counter-measures.

Algorithmic Thinking and New Digital Literacy

The article discusses the concept of algorithmic thinking in the context of the history of the formation of school informatics, in the competencies of new digital literacy and in the system of developmental education. The structure of digital literacy based on algorithmic supports is shown and an example of an educational template of algorithmic tasks for younger students is given.

On Using Real-Time and Post-Contest Data to Improve the Contest Organization, Technical/Scientific Procedures and Build an Efficient Contestant Preparation Strategy

Nowadays, the coaches of various sports disciplines use analytical tools to process the game data, analyze the behavior of their team, individual players, and build efficient strategies based on the strength and weaknesses of the competitors. Considering its global scope, time limitation, complexity of tasks, ranking, and medals, IOI can also be considered as an intellectual sports contest. With the direct relation to Information Technology and sports, the statistics of the IOI contests need to be analyzed to deliver better results, initate changes in the preparation strategy and increase the quality of the event as well. This paper provides a statistical analysis based on the last on-site IOI and shares insights on each of them.

Why You Should Know and Not Only Use Sorting Algorithms: Some Beautiful Problems

In most programming languages, the built-in (standard library) sort() function is the most convenient and efficient way for ordering data. Many software engineers have forgotten (or never knew) the underlying algorithms. In programming contests, almost all of the tasks involving sorting can be solved with only knowing how to use the sort() function. The question might arise in young students: do we need to know how it works if we only need to use it? Also, why should we know multiple efficient sorting algorithms, is not one enough? In this paper, we help the teachers to give the best answers to these questions: some beautiful tasks where the key to the solution lies in knowing a particular sorting algorithm. In some cases, the sorting algorithms are applied as a surprisingly nice idea, for example, in an interactive task or a geometry question.

Self-Generated Figures in Sequence Processing

A figure may convey an idea, an argument and even a proof, sometimes better than words. It may also elicit an idea, an argument and a proof. In problem solving, a figure may give a “feel” of a problem. A self-generated figure may help getting insight, or serve as a means for representing one’s inner associations, or mental model of the problem. This paper presents selfgenerated figures in algorithmic problem solving. Students of our IOI advanced stage demonstrated constructive utilization of self-generated figures in solving challenging sequence processing tasks. The figures elicited associations of hidden patterns, whose recognition yielded elegant and efficient algorithmic solutions. We advocate the application and examination of self-generated figures in algorithmic problem solving.

The Cuban Olympiad in Informatics: A New Stage from the DMOJ Online Judge

The Cuban Olympiad in Informatics is a competition promoted by the Ministry of Education of the Republic of Cuba and among its objectives is to encourage the study of programming and algorithms in students of pre-university education. The competition has different stages ranging from the school level to the national contest. In recent years, the programming competition has been renewed with the use of an instance of the Don Mills Online Judge, an open-source online judge. This has allowed the event to be held simultaneously from all the country’s provinces, which has been a challenge for students and teachers from the participating Cuban schools.

Automatic Makers as a Source for Olympiad Tasks

Automatic maker is meant as a device to produce (or compose) things by itself, by a model, customization or a program. Nowadays the most advanced automatic makers in mass use are 3D-printers.The purpose of the paper is to present methods of generating various Olympiad tasks by using evident images of virtual automatic makers. As a perspective, production (performing) of processes is also considered (as automatic 4D-makers). Besides of the main operation: putting a pixel (voxel), the following primitives with virtual things can be involved: cutting; gluing; putting a building block; erasing a building block; copying a fragment, (for 4D-) shifting a building block. Tasks are generated naturally: to make a given thing (perform a given simple process) optimally in any sense (with respect to time; to number of primitives; to number of building blocks etc.). Such tasks are well-understood, have short formulations and are difficult to be solved even with initial data of small volume; a “brute force” method is either inapplicable or gives too overestimate of complexity.